Barbara pictured with husband Scott Mitchell, who will run the London Marathon on April 28

He wrote: “During the interval we sneaked her into Royal Box and the response from the auditorium was so moving.

“After the show she was even tap dancing. A day I will remember.”

Last month, the TV legend made her first appearance on camera since her devastating dementia diagnosis was revealed earlier this year.

The ex-Carry On star, 81, made a personal call-to-arms video message urging people to run next year’s London Marathon for the Dementia Revolution to raise funds and change attitudes towards the condition.

Her husband, Scott Mitchell, will spend his 56th birthday running 26 miles across the capital alongside a few currently unnamed stars of EastEnders who wish to support their former colleague.

Barbara Windsor talks about Alzheimer's for the first time as she calls for people to run the 2019 London Marathon for the Dementia Revolution